Around 8,000 invited guests will descend on the royal residence to take tea in the 40 acre gardens.

Prince Philip will be joined on the Palace terrace by the Queen, Duchess of Cambridge, Duke of York, Princess Eugenie, the Princess Royal and other members of the family for the National Anthem performed by a military band.

A 41-gun salute will be fired by the King's Troop Royal Horse Artillery from London's Hyde Park at noon in celebration.

The Duke, who shows no signs of slowing down amid a packed programme of engagements, recently returned from France to mark the 70th anniversary of the D-Day landings.